Heat Pump, Small Power Station and Method of Pumping Heat

ABSTRACT

A heat pump includes a first portion for evaporating a working fluid at a first pressure, for compressing the evaporated working fluid to a second, higher pressure, and for liquefying the compressed working fluid within a liquefier, and a second portion for compressing liquid working fluid to a third pressure, which is higher than the second pressure, for evaporating the working fluid compressed to the third pressure, for relaxing the evaporated working fluid to a pressure, which is lower than the third pressure, so as to generate electrical current, and for liquefying relaxed evaporated working fluid within the liquefier.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national entry of PCT Patent ApplicationSerial No. PCT/EP2008/000875 filed 4 Feb. 2008, and claims priority toGerman Patent Application No. 102007005930.4 filed 6 Feb. 2007, whichare incorporated herein by references in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a heat pump and, in particular, to aheat pump comprising a power generation property.

FIG. 8 shows a known heat pump as is described in “TechnischeThermodynamik”, Theoretische Grundlagen and praktische Anwendungen, 14threvised edition, Hanser Verlag, 2005, pp. 278-279. The heat pumpincludes a closed cycle, within which a working substance, such as R134a, circulates. Via a first heat exchanger 80 and the evaporator, somuch heat is withdrawn from the soil, or the ground water, that theworking substance evaporates. The working substance, which now is richin energy, is extracted by the compressor via the suction line. Withinthe compressor 81, it is compressed, thus increasing pressure andtemperature. This compression is performed by a piston compressor. Theworking substance, which has been compressed and exhibits a hightemperature, now passes into the second heat exchanger 82, theliquefier. Within the liquefier, so much heat is withdrawn from theworking substance by the heating or process-water cycle that thecoolant, being subject to high pressure and high temperature, isliquefied. Within the choke or expansion member 83, the workingsubstance is expanded, i.e. the working substance is relieved of stress.Here, pressure and temperature are reduced to such an extent that theworking substance is again able to re-absorb energy from the soil or theground water within the evaporator. Now the cycle is complete and startsagain.

As can be seen from this, the working substance serves as an energytransporter so as to take up heat from the soil or ground water, and togive it off, within the liquefier, to the heating cycle. In this processmanagement, the 2nd law of thermodynamics is complied with, said lawstating that heat or energy only be transferred, “on its own”, can froma higher temperature level to a lower temperature level, and thatinversely this may also occur by means of energy supply from outside,here by the driving work of the compressor.

FIG. 7 shows a typical h, log p diagram (h is the enthalpy, p thepressure of a material). An isobaric evaporation of the workingsubstance takes place, between point 4 and point 1 in the diagram ofFIG. 7, at low values for the pressure and the temperature (p1, T1).Here, the heat Q81 is supplied.

Ideally, a reversible compression of the working substance vapor to apressure of p2 is performed, between point 1 and point 2, within anadiabatic compressor. The temperature rises to T2 in the process. A workof compression is to be supplied here.

Then, isobaric cooling of the working substance vapor from 2 to 2′ isperformed at a high pressure p2. Overheating is reduced. Subsequently,the working substance is liquefied. Overall, the heat Q25 can bedissipated.

Within choke 83, the working substance is choked, in an adiabaticmanner, from the high pressure p2 to the low pressure p1. In theprocess, part of the liquid working substance evaporates, and thetemperature falls to the evaporating temperature T1. In the h, log pdiagram, the energies and characteristics of this process may becalculated by means of enthalpies, and may be illustrated, as is shownin FIG. 7.

The working fluid of the heat pump thus takes up, within the evaporator,heat from the surroundings, i.e. air, water, waste water or the soil.The liquefier serves as a heat exchanger for heating up a heatingsubstance. Temperature T1 is slightly lower than the ambienttemperature, temperature T2 is considerably higher and temperature T2′slightly higher than the heating temperature involved. The higher thetemperature difference called for, the more work may be effected by thecompressor. Therefore, it is desired to keep the rise in temperature assmall as possible.

Thus, with regard to FIG. 7, a compression of the working materialvapors is performed, in the ideal case, along the curve for the entropys =constant up to point 2. From here up to point 3, the working materialliquefies. The length of the distance 2-3 represents the useful heat Q.From point 3 to point 4, the working material is expanded, and frompoint 4 to point 1, it is evaporated, the distance 4-1 reflecting theheat withdrawn from the heat source. Unlike the T, s diagram, themagnitudes of the heat and of the work may be taken as distances in theh, log p diagram. Pressure losses within valves, within the pressure andsuction lines, of the compressor, etc. change the ideal curve of thecyclic process in the h, log p diagram and reduce the effectiveness ofthe entire process.

With piston compressors, the working material vapor which has beensucked in initially has a lower temperature than the cylinder wall ofthe compressor, and thus absorbs heat from it. As the compressionincreases, the temperature of the working material vapor eventuallyincreases to exceed that of the cylinder wall, so that the workingmaterial vapor gives off heat to the cylinder wall. Then, when thepiston again sucks in and compresses vapor, the temperature of thepiston wall is initially fallen below again and then exceeded, whichleads to constant losses. In addition, overheating of the workingmaterial vapor which has been sucked in will be called for and usefulfor the compressor to no longer suck in any liquid working material.What is also disadvantageous, in particular, is the heat exchange withthe oil cycle of the piston compressor, which is indispensable forlubrication.

Any irreversible processes, such as heat losses during compression,pressure losses within the valves, and flow losses within the pressureline for liquefying and within the liquefier, will increase the entropy,i.e. the heat which cannot be retrieved. In addition, temperature T2,also exceeds the liquefying temperature. Such an “overheating enthalpy”is undesired, in particular because the high temperatures occurring inthe process will accelerate the aging of the compressor and, inparticular, of the lubricating oil within a piston compressor. Also, theeffectiveness of the process is reduced.

The liquefied working material at a low temperature at the output of theliquefier would have to be expanded, within the context of an idealcyclic process, via an engine, for example a turbine, so as to exploitthe excess energy which was present in comparison with the state presentat the temperature and the pressure prior to compressing. Because of thegreat expenditure involved for this, this measure is dispensed with, andthe pressure of the working material is abruptly reduced to the lowpressure and the low temperature by the choke 83. The enthalpy of theworking material remains approximately the same in the process. Due tothe abrupt pressure reduction, the working material may partiallyevaporate to reduce its temperature. The evaporation heat that may beused is derived from the working material exhibiting excess temperature,i.e. is not withdrawn from the heat source. The entirety of the lossescaused by the expansion within choke 83 (FIG. 8) is referred to asexpansion losses. These are exergy losses because heat of a temperatureT is converted to heat of a temperature T0. These losses may be reducedif the liquid working material can dissipate its heat to a medium havinga temperature smaller than T. This undercooling enthalpy may beexploited by an internal heat exchange which, however, also involvesadditional expenditure in terms of equipment. Also in principle, theinternal heat exchange has its limitation, because in the compression ofthe vapors, the overheating temperature T2 increases, whereby the gainsachieved are partly cancelled out, and because also more thermal strainis put on the machine and the lubricating oil. Eventually, theoverheating causes the volume of the vapor to increase, whereby thevolumetric heat power decreases. This heat is utilized for preheatingthose vapors of the working material which flow to the compressor, onlyto the extent useful in order to be sure that all droplets contained inthe vapor of the working medium are converted to vapor.

In general, one may state that the ratio of the enthalpy differencebetween point 1 and point 4 and the enthalpy difference between point 2and point 1 of the h, log p diagram is a measure of the economicefficiency of the heat pump process.

A working substance which is currently popular is R134a, the chemicalformula of which is CF3-CH2F. It is a working substance which, eventhough it is no longer damaging to the ozone layer, nevertheless has animpact, in terms of the greenhouse effect, which is 1000 times higherthan that of carbon dioxide. However, the working substance R134a ispopular since it has a relatively large enthalpy difference of about 150kJ/kg.

Even though this working substance is no longer an “ozone killer”, thereare nevertheless considerable requirements placed upon the completenessof the heat pump cycle, to the effect that no molecules of the workingsubstance will escape from this closed cycle, since they would causeconsiderable damage due to the greenhouse effect. This encapsulationleads to considerable additional cost when building a heat pump.

Also, one may assume that by the time the next stage of the KyotoProtocol is implemented, R134a will be prohibited by the year 2015because of the greenhouse effect, which has also happened to previous,considerably more damaging substances.

What is therefore disadvantageous about existing heat pumps, beside thefact of the harmful working substance, is also the fact that, due to themany losses within the heat pump cycle, the efficiency factor of theheat pump typically does not exceed a factor of 3. In other words, 2times the energy that has been used for the compressor may be withdrawnfrom the heat source, such as the ground water or the soil. Whenconsidering heat pumps wherein the compressor is driven by electricalcurrent, and when considering, at the same time, that the efficiencyfactor in current generation is perhaps 40%, one will find that—withregard to the overall energy balance—the use of a heat pump is veryquestionable. In relation to the source of primary energy, 120%=3·40% ofheat energy are provided. A conventional heating system using a burnerachieves efficiency factors of at least 90-95%, i.e. an improvement ofonly 25-30% is achieved at high technical and, therefore, financialexpense.

Improved systems use primary energy for driving the compressor. Thus,gas or oil is burned to provide the compressor rating using the energyreleased by combustion. What is advantageous about this solution is thefact that the energy balance actually becomes more positive. The reasonfor this is that even though only about 30% of the source of primaryenergy may be used as driving energy, the waste heat of, in this case,about 70% can also be used for heating. The heating energy provided willthen amount to 160%=3·30%+70% of the source of primary energy. What isdisadvantageous about this solution, however, is that a household maynevertheless use a combustion engine and a fuel store even though it hasno longer a classical heating system. The expenditure made for engineand fuel storage may be added to the expense made for the heat pump,which, after all, is a highly closed cycle due to the coolant beingharmful to the climate.

All of these things have resulted in that heat pumps have had onlylimited success in competition with other types of heating systems.

Consequently, a heat pump is characterized in that mechanical energy isinput into a system, and thermal energy at a higher temperature level isoutput. The outcome of the heat pump is positive when the energy outputat the high temperature level is at least higher than the electricalenergy employed for compression. In this context, it may obviously betaken into account that—when one assumes primary energy consumption asthe basis—the electrical energy also has been generated only at alimited efficiency factor, for example by means of a combustion process.

On the other hand, thermal energy is withdrawn from the heat source bythe evaporating refrigerant in a closed cycle in refrigerating plants,said thermal energy is pumped, by using mechanical energy, to a highertemperature level by means of a compressor and is finally condensedagain so as to dissipate the thermal energy to the heat sink in additionto the mechanical energy. This, too, is referred to as a heat pump.Typically, the pressure employed is overpressure in relation toatmospheric pressure.

Also in large-scale plants such as nuclear power stations, for example,water is evaporated in that primary energy is converted to heat whichevaporates water, as a result of which steam turbines are driven, whichin turn drive a generator. The water vapor is condensed in enormouscooling towers to retrieve the water. Electrical or mechanical energyand waste heat are formed in the process. In addition to politicalproblems, an essential disadvantage of such a power station are also theenormous manufacturing costs and the decentralized operation associatedtherewith.

DE OS 2745127 discloses a method of driving a heat pump or refrigeratingmachine wherein a mass flux is heated up within a heat exchanger and issupplied to an expansion machine as liquid or saturated steam. Theexpansion machines drives a compression machine which compresses a steamdrawn in by an evaporator. The compressed steam is fed to a capacitor.The expansion machine and the compression machine are mechanicallycoupled.

SUMMARY

According to an embodiment, a heat pump may have: a first portion forevaporating a working fluid at a first pressure, for compressing theevaporated working fluid to a second, higher pressure, and forliquefying the compressed working fluid within a liquefier; and a secondportion for compressing liquid working fluid to a third pressure, whichis higher than the second pressure, for evaporating the working fluidcompressed to the third pressure, for relaxing the evaporated workingfluid so as to generate electrical current, and for liquefying relaxedevaporated working fluid within the liquefier.

According to another embodiment, a method of pumping heat may have thesteps of: operating a first portion, operating the first portionincluding evaporating a working fluid at a first pressure, compressingthe evaporated working fluid to a second, higher pressure, andliquefying a compressed working fluid within a liquefier; or operating asecond portion, the operation of the second portion includingcompressing liquid working fluid to a third pressure, which is higherthan the second pressure, evaporating the working fluid which has beencompressed to the third pressure, relaxing the evaporated working fluidto a pressure smaller than the third pressure, so as to generateelectrical current, and liquefying relaxed evaporated working fluidwithin the evaporator.

According to another embodiment, a small power station for heatingbuildings may have: a water pump for compressing water to a firstpressure above 0.1 MPa; an evaporator for evaporating the compressedwater using primary energy from a combustion process or from a solarcollector so as to provide water vapor at the first pressure; a turbinefor generating electrical current, the turbine being configured to bringwater vapor up to a second pressure while outputting electrical current,the second pressure being smaller than 50 kPa; and a liquefier forliquefying the cooled-off water vapor, the liquefier including a heatingadvance flow and a heating backflow for heating a building.

According to another embodiment, a method of heating a building may havethe steps of: compressing water to a first pressure above 0.1 MPa;evaporating the compressed water while using primary energy from acombustion process or from a solar collector, so as to provide watervapor at the first pressure; generating electrical current by relaxingthe water vapor at the first pressure to a second pressure, the secondpressure being smaller than 50 kPa; and liquefying the water vapor,which has been output by generating electrical current, within aliquefier water volume coupled to a heating advance flow and a heatingbackflow for heating a building.

The present invention is based on the finding that a heat pump having afirst portion, by means of which thermal energy at a relatively hightemperature level is obtained by compressing steam using mechanicalenergy, may be ideally combined with a second portion, wherein a liquidworking fluid is compressed, and wherein the liquid working fluid, whichis subject to a relatively high pressure, is evaporated using anexternal source of energy. The steam which is highly pressurized is thenrelaxed via a turbine, which results in electrical energy; then thesteam leaving the turbine—which is at a low pressure and a comparativelylow temperature—is fed to the same liquefier which acts as a liquefieralso in the first portion of the heat pump. Thus, the inventive heatpump comprises three different pressure zones. The first pressure zoneis the zone having the lowest pressure, wherein the working fluid isevaporated at a low pressure and, thus, at a low temperature. In anadvantageous embodiment of the invention, the pressure of this lowpressure zone exhibits values of less than 20 hPa.

Compression of the steam leads to compressed water vapor, which has asecond, higher pressure. Due to the compression of the steam, thetemperature of the steam rises to the higher temperature level; due tothe liquefaction of the compressed steam, heat may be extracted from thesteam and may be used for heating buildings, for example. The secondpressure is at least 5 hPa higher than the first pressure, and typicallyis even about double the first pressure.

Unlike the first portion, no steam, but a liquid working fluid iscompressed in the second portion of the heat pump; to achieve this,relatively low-cost devices are sufficient in contrast to thecompression of steam, namely typically water pumps having a powerconsumption of a few Watt. The third pressure exhibited by thepressurized water amounts to 0.5 to 3 MPa, which corresponds toevaporation temperatures of about 120 to 235 degrees Celsius in the caseof water.

While external energy is supplied, the pressurized water is evaporated,said external energy being a waste gas stream of a burner, or a heatdissipation of a solar collector. The hot steam, which is highlypressurized and which is particularly high especially in comparison withthe area of low pressure, which exhibited by the liquefier, namely ishigher by a factor of 500, for example, is relaxed down to thelow-pressure area via a turbine, wherein there is also a lowtemperature, which area also exhibits a temperature in the order ofmagnitude of from 30 to 40 degrees, which may readily be used forfeeding an underfloor heating system.

In accordance with the present invention, therefore, in the secondportion of the heat pump the externally provided energy is used, on theone hand, for generating electrical current which may either be fed intothe power supply network or which may drive the compressor of the firstheat pump portion, or which is at least partly fed into the power supplynetwork and may partly drive the compressor, and additionally, thermalenergy is obtained within the liquefier, said thermal energy beingreadily usable for heating buildings. What is advantageous is inparticular that a working fluid steam is present at the output of theturbine, said steam being relatively similar, in terms of itstemperature and pressure properties, to the working fluid steam which isgenerated by means of compression from the pressure area exhibiting thefirst low pressure.

Thus, in accordance with the invention, energy is extracted from a heatsource by means of evaporation, it being possible for this heat pump tobe a solar collector, a wood-fired oven, a pellet oven or any otherburner. This energy is partly converted to mechanical energy, theremainder being supplied to a heat sink during liquefaction. This heatsink is identical with a typical heat sink of a heat pump based on vaporcompression, as is favorable for heating buildings, for example.

Advantageously, water is used as the working liquid or refrigerant, alow-pressure area already being present due to the first portion of theheat pump, said low-pressure area ensuring that a high pressuredifference is obtained, namely between the high pressure exhibited bythe vapor which is generated due to the external heat supply, and thelow pressure existing within the liquefier. This low-pressure areaenables the process employed to be utilized on a smaller scale, namelyfor heating buildings, and thus to be employed in a decentral manner andwith all of the advantages.

In addition, it is advantageous to switch in the first portion of theheat pump and to triple the heating energy which may thus be achievedand which is contained within a primary energy source. This is achievedin that the energy released by the combustion is not directly used forheating water, but is employed to evaporate the highly pressurizedwater, which results in that, due to the relaxation to thesecond-pressure area, electrical current is generated which is then atleast partly used for compressing the vapor employed in the first heatpump portion.

In advantageous embodiments, water is used in the first and secondportions. In comparison with the working substance R134a, which isfrequently used these days, water additionally has a considerably largerratio of the enthalpy differences. The enthalpy difference, which isdecisive in terms of how effective the heat pump process is, amounts toabout 2500 kJ/kg for water, which is about 16 times as much as theusable enthalpy difference of R134a. The compressor enthalpy to beexpended, by contrast, is only 4-6 times as large, depending on theoperating point.

In addition, water is not harmful to the climate, i.e. is neither anozone killer, not does it aggravate the greenhouse effect. This enablesheat pumps to be built in a considerably simpler manner, since therequirements placed upon the completeness of the cycle are not high.Instead, it is even advantageous to completely leave behind the closedprocess and to make an open process instead, wherein the ground water,or the water representing the exterior heat source, is directlyevaporated.

Advantageously, the evaporator is configured such that it comprises anevaporation chamber within which the evaporation pressure is lower than20 hPa (hectopascal), so that water will evaporate at temperatures below18° C. and, advantageously, below 15° C. In the northern hemisphere,typical ground water has temperatures of between 8 and 12° C., whichinvolves pressures of below 20 hPa for the ground water to evaporate, soas to be able to achieve, by evaporating the ground water, a reductionin the temperature of the ground water and, thus, heat removal, by meansof which a heating system within a building, such as a floor heatingsystem, may be operated.

In addition, water is advantageous in that water vapor takes up a verylarge volume, and in that one need no longer fall back on a displacementmachine such as a piston pump or the like in order to compress the watervapor, but that a high-performance compressor in the form of adynamic-type compressor, such as a radial-flow compressor, may beemployed which is highly controllable in terms of its technology and iscost-efficient in terms of its production since it exists in highquantities and has been used up to now as a small turbine or as aturbocompressor in cars, for example.

A prominent representative of the pedigree of dynamic-type compressorsas compared to displacement machines is the radial-flow compressor, forexample in the form of a turbocompressor comprising a radial-flow wheel.

The radial-flow compressor, or the dynamic-type compressor, may achieveat least such a level of compression that the output pressure exitingfrom the radial-flow compressor is at least 5 hPa higher than the inputpressure into the radial-flow compressor. Advantageously, however, acompression will have a ratio larger than 1:2, and even larger than 1:3.

Compared to piston compressors, which are typically employed withinclosed cycles, dynamic-type compressors additionally have the advantagethat the compressor losses are highly reduced, due to the temperaturegradient existing within the dynamic-type compressor, as compared with adisplacement machine (piston compressor), wherein such a stationarytemperature gradient does not exist. What is particularly advantageousis that an oil cycle is completely dispensed with.

Moreover, multi-stage dynamic-type compressors may be particularly usedto achieve the relatively high level of compression which should have afactor of 8 to 10 in order to achieve sufficient advance flowtemperature in a heating system even for cold winter days.

In an advantageous embodiment, a fully open cycle is employed, whereinthe ground water is made to have the low pressure. An advantageousembodiment for generating a pressure below 20 hPa for ground waterconsists in the simple use of a riser pipe leading to a pressure-tightevaporation chamber. If the riser pipe overcomes a height of between 9and 10 m, the evaporation chamber will comprise the low pressure thatmay be used at which the ground water will evaporate at a temperature ofbetween 7 and 12° C. Since typical buildings are at least 6 to 8 m inheight and since in many regions, the ground water is present already at2 to 4 m below the surface of the earth, installing such a pipe leads tono considerable additional expense since one may only dig a littledeeper than for the foundations of the house, and since typical heightsof buildings are readily high enough for the riser pipe or theevaporation chamber not to protrude above the building.

For cases of application wherein only a shorter riser pipe is possible,the length of the riser pipe may be readily reduced by a pump/turbinecombination which only involves a minor amount of additional work fromthe outside due to the fact that the turbine is used for converting thehigh pressure to the low pressure, and the pump is used for convertingthe low pressure to the high pressure.

Thus, primary heat-exchanger losses are eliminated, since no primaryheat exchanger is used but use is made of the evaporated ground waterdirectly as a working vapor or a working substance.

In an advantageous embodiment, no heat exchanger is used even in theliquefier. Instead, the water vapor which is heated up due to beingcompressed is directly fed into the heating-system water within aliquefier, so that within the water, a liquefaction of the water vaportakes place such that even secondary heat-exchanger losses areeliminated.

The advantageously utilized water evaporator/dynamic-typecompressor/liquefier combination thus enables efficiency factors of atleast 6 in comparison with common heat pumps. Thus, it is possible towithdraw from the ground water at least 5 times the amount of theelectric energy spent for compression, so that a heating energy of240%=6·40%, in relation to the source of primary energy, is providedeven if the dynamic-type compressor is operated with electrical current.As compared with the prior art, this represents at least double theefficiency or half of the energy costs. This is particularly true forthe emission of carbon dioxide, which is relevant in terms of theclimate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be detailed subsequentlyreferring to the appended drawings, in which:

FIG. 1 a is a basic block diagram of the inventive heat pump;

FIG. 1 b is a table for illustrating various pressures and theevaporation temperatures associated with these pressures;

FIG. 1 c is a schematic overview of a small power station;

FIG. 1 d is a schematic overview of the heat pump having the firstportion and the second portion in accordance with an embodiment;

FIG. 2 is a block diagram of an advantageous embodiment of the inventiveheat pump having the first portion which is operated with ground water,sea water, etc, and having the second portion which may be employed forpower generation;

FIG. 3 a is an alternative embodiment of the liquefier of FIG. 2;

FIG. 3 b is an alternative embodiment of the liquefier with a reducedbackflow in the off operation;

FIG. 3 c is a schematic representation of the liquefier having a gasseparator;

FIG. 4 a is an advantageous implementation of the evaporator of FIG. 2;

FIG. 4 b is an alternative embodiment of the evaporator using theliquefier drain as a boiling assistance;

FIG. 4 c is an alternative embodiment of the evaporator having a heatexchanger for using ground water for boiling assistance;

FIG. 4 d is an alternative embodiment of the evaporator comprisingfeeding from the side and draining in the center;

FIG. 4 e is a schematic representation of the expander with anindication of advantageous measurements;

FIG. 5 a is an alternative implementation of the evaporator for reducingthe height of the riser pipe;

FIG. 5 b is an implementation of an alternative realization ofconnecting a heating line to the liquefier with a turbine/pumpcombination;

FIG. 6 a is a schematic representation of the compressor performed byseveral dynamic-type compressors arranged one behind the other;

FIG. 6 b is a schematic representation of the setting of the numbers ofrevolutions of two cascaded dynamic-type compressors as a function ofthe target temperature;

FIG. 6 c is a schematic top view of a radial-flow wheel of adynamic-type compressor in accordance with an advantageous embodiment ofthe present invention;

FIG. 6 d is a schematic cross-sectional view with a merely schematicalrepresentation of the radial-wheel vanes for illustrating the differentexpansions of the vanes with regard to the radius of the radial-flowwheel;

FIG. 7 is an exemplary h, log p diagram; and

FIG. 8 is a known heat pump performing the left-handed cycle of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

Before providing a more detailed explanation of the subject matter ofthe present invention with reference to FIGS. 1 c and 1 d and FIG. 2,the first portion of an inventive heat pump shall be presented withreference to FIGS. 1 a and 1 b.

FIG. 1 a shows an inventive heat pump which initially comprises a waterevaporator 10 for evaporating water as a working fluid so as togenerate, on the output side, a vapor within a working vapor line 12.The evaporator includes an evaporation chamber (not shown in FIG. 1 a)and is configured to generate, within the evaporation chamber, anevaporation pressure lower than 20 hPa, so that the water will evaporatewithin the evaporation chamber at temperatures below 15° C. The water isadvantageously ground water, brine circulating freely within the soil orwithin collector pipes, i.e. water with a specific salt content, riverwater, lake water or sea water. In accordance with the invention, alltypes of water, i.e. limy water, non-limy water, saline water ornon-saline water, are advantageously used.

This is due to the fact that all types of water, i.e. all of these“water materials”, have the favorable property of water, i.e. consistingin that water, also known as “R 718”, has an enthalpy-difference ratioof 6 usable for the heat pump process, which corresponds to more thandouble a typically usable enthalpy-difference ratio of, e.g., R134a.

The water vapor is fed, by suction line 12, to a compressor/liquefiersystem 14 comprising a dynamic-type compressor, such as a radial-flowcompressor, for example in the form of a turbocompressor designated by16 in FIG. 1 a. The dynamic-type compressor is configured to compressthe working vapor to a vapor pressure of at least more than 25 hPa. 25hPa correspond to a liquefying temperature of about 22° C., which mayalready be a sufficient heating-system advance flow temperature of afloor heating system, at least on relatively warm days. In order togenerate higher advance flow temperatures, pressures of more than 30 hPamay be generated using dynamic-type compressor 16, a pressure of 30 hPahaving a liquefying temperature of 24° C., a pressure of 60 hPa having aliquefying temperature of 36° C., and a pressure of 100 hPacorresponding to a liquefying temperature of 45° C. Floor heatingsystems are designed to be able to provide sufficient heating with anadvance flow temperature of 45° C. even on very cold days.

The dynamic-type compressor is coupled to a liquefier 18 which isconfigured to liquefy the compressed working vapor. By the liquefaction,the energy contained within the working vapor is fed to the liquefier 18so as to be fed to a heating system via the advance flow 20 a. Viabackflow 20 b, the working fluid flows back into the liquefier.

In accordance with the invention, it is advantageous to extract the heat(heat energy) from the high-energy water vapor directly by the colderheating water, said heat (heat energy) being taken up by theheating-system water so that the latter heats up. In the process, somuch energy is extracted from the vapor that same becomes liquefied andalso participates in the heating cycle.

Thus, a loading of material into the liquefier, or the heating system,takes place, the loading being regulated by a drain 22, such that theliquefier in its liquefaction chamber has a water level which remainsbelow a maximum level despite the constant supply of water vapor and,thereby, of condensate.

As has already been explained, it is advantageous to take an open cycle,i.e. to evaporate the water, which represents the heat source, directlywithout a heat exchanger. Alternatively, however, the water to beevaporated could also initially be heated up by an external heat sourcevia a heat exchanger. However, what is to be taken into account in thiscontext is that this heat exchanger again signifies losses andexpenditure in terms of apparatus.

In addition, it is advantageous, in order to avoid losses for the secondheat exchanger which has been present so far on the liquefier side, touse the medium directly even there, i.e. to let the water, which comesfrom the evaporator, circulate directly within the floor heating system,when considering a house comprising a floor heating system.

Alternatively, however, a heat exchanger may be arranged, on theliquefier side, which is fed with the advance flow 20 a and whichcomprises the backflow 20 b, this heat exchanger cooling the waterpresent within the liquefier, and thus heating up a separate floorheating liquid which will typically be water.

Due to the fact that the working medium used is water, and due to thefact that only the evaporated portion of the ground water is fed intothe dynamic-type compressor, the degree of purity of the water isirrelevant. Just like the liquefier and, as the situation may be, thedirectly coupled floor heating system, the dynamic-type compressor isprovided with distilled water such that, in comparison with present-daysystems, the system has a reduced maintenance expenditure. In otherwords, the system is self-cleaning, since the system is only ever fedwith distilled water, and since the water within the drain 22 is thusnot contaminated.

In addition, it shall be noted that dynamic-type compressors have theproperties that—similar to a turbine of an airplane—they do not contactthe compressed medium with problematic materials such as oil. Instead,the water vapor is compressed only by the turbine or theturbocompressor, but is not contacted with oil or any other mediumnegatively affecting its purity, and thus is not contaminated.

The distilled water dissipated through the drain may thus be readilyre-fed to the ground water—if no other regulations are in the way.Alternatively, however, it may also be made to seep away, e.g. in thegarden or in an open area, or it may be fed to a waste waterpurification plant via the sewage system, if the regulations permit.

The inventive combination of water as a working substance with theuseful enthalpy-difference ratio which is doubly improved as comparedwith R134a, and due to the consequently reduced requirements placed uponthe closed nature of the system (rather, an open system is advantageous)and due to the use of the dynamic-type compressor, by means of which theuseful compression factors are efficiently achieved without any negativeeffects on the purity, an efficient heat pump process which is neutralin terms of environmental damage is provided which will become even moreefficient if the water vapor is directly liquefied within the liquefier,since, in this case, maybe not one single heat exchanger might be usedin the entire heat pump process.

In addition, any losses associated with the piston compression aredispensed with. In addition, the losses, which are very low in the caseof water and which otherwise occur in the choking, may be used toimprove the evaporation process, since the drain water having the draintemperature, which will typically be higher than the ground watertemperature, is advantageously used to trigger a bubble evaporationwithin the evaporator by means of a structuring 206 of a drain pipe 204,as will be explained in FIG. 4 a, in order to increase the evaporationefficiency.

FIG. 1 c shows the second portion of the inventive heat pump, which mayalso be employed, however, as a small power station for heatingbuildings without the first portion shown in FIG. 1 a.

In particular, the second portion comprises the same liquefier 18represented by means of

FIG. 1 a and coupled to a heating advance flow 20 a and a heatingbackflow 20 b. The drain 22 of the liquefier is no, longer supplied tothe channel or the primary side, in accordance with the second portionof the inventive heat pump, but is supplied to a water pump 1100 whichraises the water output by the liquefier 18 to a pressure of, e.g., 2MPa. This pressure of 2 MPa corresponds to 20 bar. Since the water pump1100 only achieves liquid compression, the temperature of the water doesnot change by the activity of the water pump.

Since water or, generally, liquid working fluids may be pressurized in asimple manner, the water pump that may be used need only be a low-costpump having a power consumption of a few watts, such as 1 to 2 watts.

The pressurized water is supplied to a water evaporator 1102. The waterevaporator 1102 obtains energy from a primary heating, such as a burnerfor wood, wood pellets, oil, gas, etc., or from a solar collector, as isschematically depicted by an energy feed line 1104. The high temperaturethat may be used for evaporating the highly pressurized water may bereadily generated by means of a combustion process. Even modern solarcollectors readily provide temperatures higher than 150° C., or evenaround 200° C., said temperatures already sufficing to evaporate waterwhich is held at a pressure of 16 bar, or has pressurized to a level of16 bar by the water pump 1100.

Therefore, highly pressurized, hot vapor is present at the output of thewater evaporator 1102, said vapor being optimally suited to be relaxedvia a turbine means, which is advantageously configured as a stageturbine. The relaxation via the stage turbine may be converted toelectrical current while using corresponding devices, for example usingknown generators, said electrical current being output from the turbine1106 via a power supply line 1108. Thus, an evaporated working fluid ispresent at the output of the turbine/generator combination 1106, whichwill simply be referred to as the “turbine” below, said evaporatedworking fluid having the low second pressure and further having atemperature which is suited to heat the working fluid present in aliquid form, which is present in the liquefier, by means ofcondensation, or liquefaction.

This thermal energy, which is emitted within the liquefier 18 by thevapor generated at the output of the turbine 1106, may readily be usedfor reaching a heating system within a building, namely via the heatingadvance flow 20 a and/or the heating backflow 20 b. The heating systemwithin a building may operate without a heat exchanger, which ispossible when the working fluid is directly supplied, in a liquid form,to a heating system, such as radiators or underfloor heaters without theliquid cycle within the radiators or underfloor heater being separatedfrom the liquid volume of the liquefier by a heat exchanger.

However, a heat exchanger may alternatively be provided, which is usefulwhen working fluids other than water are employed, as will be explainedwith reference to FIG. 1 d. However, for a small power station forheating buildings, it is advantageous to use water as the workingliquid, and to have pressure ranges which correspond to the evaporationtemperatures of water at the corresponding pressures.

An example referring to size is shown in FIG. 1 c. The volume flow rateof water is 4 ml per second, and it is assumed that the liquefier drainhas a temperature of 36° C. The resulting pressure within the liquefieris thus at 60 mbar or 60 hPa, as is depicted in FIG. 1 b. The waterhaving a pressure of 60 mbar is brought up to a pressure of 20 bar, or 2MPa, by means of the water pump 1100, which corresponds to a factor of333. This pressure difference is sufficiently large for using theinventive process to drive a turbine 1106 to generate electricalcurrent. Generally, pressure differences larger than a factor 50 lead toan advantageous yield of electrical energy, it also being possible forthe pressure differences to take on very high values if the water pump1100 is designed for this and if the energy supply via the schematicenergy feed line 1104 has a sufficiently high temperature for the highlypressurized water to be evaporated, and for generating, at the output ofthe water evaporator 1102, the vapor which has a high temperature and ahigh pressure and is therefore ideally suited to drive a turbine andthus to generate electrical current 1108. In the example shown in FIG. 1c, the vapor has a temperature of 215° C. and a pressure of 2 MPa, or 20bar. The turbine 1106 is dimensioned such that it outputs a workingvapor having a temperature of 36° C. and a pressure of 60 mbar. With thevolume flow rate shown and the pressure and/or temperature differencesdepicted, electrical current may be generated in the order of magnitudeof 1.5 kW. In addition, the liquefier liquid volume is heated up by thecondensed vapor at the same time, so that, in addition to the currentgain, advantageous heating of buildings is also achieved.

In advantageous embodiments, the rate of the volume flow through thesystem, i.e. the volume flow rate, of working fluid within the line 22ranges from 1 ml per second to 100 ml per second. The second pressure,i.e. the pressure exhibited by the vapor within the liquefier andexhibited by the water at the output of the liquefier advantageouslyranges from 25 hPa to 0.1 MPa, and the pressure generated by the waterpump advantageously is above around 5 bar, and in particularlyadvantageous embodiments is in a range above around 12 bar.

The temperature exhibited by the vapor at the output of the waterevaporator 1102 and/or at the output of the stage turbine 1106 resultsfrom the corresponding pressure of the vapor, as is depicted in thetable of FIG. 1 b and as is also depicted in the further table in FIG. 1d for larger pressures for some working points.

In advantageous embodiments, the proper refrigerant is combined with theproper working pressures. Water condenses as early as at 22° C. in anunderpressure atmosphere of 26 mbar, or at 100° C. at about 1.01 bar. Bybeing condensed, the water passes on its condensation energy to theheating-system water, which is advantageously used directly for heatingbuildings. The under-cooled water in the heating backflow is pressurizedto the high working pressure by the feed pump 1100. Within the waterevaporator, which advantageously comprises a heat exchanger, the waterevaporates and thus ensures a temperature which corresponds to thepressure. At 100° C., the pressure is 1 bar. At 200° C., the pressure is16 bar, and at 300° C., the pressure is 90 bar. The overpressure is usedfor driving the turbine 1106 so as to convert the mechanical energy,which has been absorbed due to the gas flow, to electrical energy, forexample. The vapor flows from the high-pressure side to the low-pressureside, and the cycle starts again. If the condensation heat is notsufficient for heating the building, it is advantageous to additionallyoperate the first heat pump portion; for this purpose, either theelectrical current generated by the turbine 1106 is used, or electricalcurrent is obtained from the power supply network. The latter case maybe more favorable if the current obtained from the power supply networkis lower in cost than the current output to the power supply network.

Thus, by burning a piece of wood, about three times the amount ofthermal energy may be provided for heating buildings than if the woodhad been used directly for heating the building. This is due to the factthat the energy contained within the piece of wood is employed to drivethe first portion of the heat pump.

While FIG. 1 c depicts an advantageous embodiment of the small powerstation for heating buildings, FIG. 1 d shows an advantageous embodimentof the inventive heat pump comprising the first portion and the secondportion.

The first portion comprises the evaporator 10 for evaporating a workingfluid at the first (low) pressure. In addition, the first portioncomprises the dynamic-type compressor 16 for compressing the evaporatedworking fluid to a second, higher pressure. Eventually, the firstportion also comprises the liquefier 18 for liquefying the compressedworking fluid.

In accordance with the invention, the second portion is furtherprovided, by means of the water pump 1100, for compressing a liquidworking fluid to a third pressure, which is higher than the secondpressure. In addition, the second portion serves to evaporate theworking fluid, which has been compressed to the third pressure, by meansof the evaporator or heat exchanger 1102. In addition, the secondportion serves to relax the evaporated working fluid, via a turbine1106, to a pressure smaller than the third pressure so as to generatethe electrical current which may be output via a line 1108. Moreover,the second portion also comprises the liquefier 18 so as to liquefy therelaxed evaporated working fluid within the liquefier 18.

The working fluid within the first and second portions of the heat pumpof FIG. 1 d in accordance with the present invention are identical if,as is shown in FIG. 1 d, there is a working fluid contact within theliquefier, i.e. if, as is shown in FIG. 1 d, no heat exchanger isemployed with regard to the liquefier 18. However, liquefaction mayobviously also take place such that the cycles of the working fluidswithin the second and first portions are fluidically separated from eachother, while, however, both cycles within the liquefier are thermallycoupled. However, it is advantageous to employ one and the same workingfluid and not only a thermal, but also a fluidic coupling within theliquefier 18, since in this case no heat exchangers might be used, butthe output line of the turbine 1106 may be directly coupled into theliquefier or, via a simple coupler 1110, to the liquefier.

The coupler 1110 is configured to receive, on the input side, both theoutput line of the dynamic-type compressor 16 of the first portion andthe output line of the turbine 1106 of the second portion, while theoutput of the coupler 1110 is coupled to the liquefier 18. Depending onthe implementation, the coupler may connect either the output of thedynamic-type compressor 16 or the output of the turbine 1106 to theoutput, or the coupler may connect both outputs to the liquefier 18 inparallel, depending on the requirement and implementation of thedynamic-type compressor.

In addition, the liquefier 18 is coupled to the water evaporator 10 viaa switch 1114, which may be configured to represent a normal drain whenthe second portion of the heat pump is deactivated.

Alternatively, when the second portion is deactivated, the drain water22 may be directly fed into the primary-side evaporator cycle, as isshown in FIG. 2.

The switch 1140 may further be implemented to provide both the waterpump 1100 and the water evaporator 10 with liquid. This is due to thefact that the advantageous implementation of the first portionrepresents an open cycle, since working fluid is taken from theenvironment, for example from ground water, and is recycled back to theenvironment somewhere else, whereas the cycle occurring in the secondportion is a closed cycle, since liquefier water may again and again becompressed, evaporated, relaxed and liquefied. Alternatively, however,both the first cycle and the second cycle within the first portion andthe second portion, respectively, may be configured as open cycles. Thisis possible when the working fluid is water, i.e. when no contaminationtakes place, as is not the case, in particular, when a radial-flow wheelis employed as the dynamic-type compressor, and when advantageously astepped turbine which is provided with radial-flow wheels is employed asthe turbine.

The second portion of the inventive heat pump advantageously furthercomprises the controller 1112 so as to utilize the electrical currentgenerated at the output line 1108. Depending on the implementation, thecurrent may be directly utilized to drive the dynamic-type compressor16. Alternatively, the electrical current generated by the turbine 1108may also be fed into the power supply network for a fee, while thecurrent of the dynamic-type compressor is also obtained from the powersupply network for money. This approach is economically useful, inparticular, when the fee obtained for feeding in current into the powersupply network is higher than the fee to be paid for current obtainedfrom the power supply network.

In addition, the current generated by the turbine may at least partly beused for driving the water pump 1100.

An advantageous embodiment of the present invention will be explainedbelow in detail with reference to FIG. 2. The water evaporator comprisesan evaporation chamber 100 and a riser pipe 102, wherein ground waterfrom a ground water reservoir 104 moves upward into the evaporationchamber 100 in the direction of an arrow 106. The riser pipe 102 leadsto an expander 108 configured to expand the relatively narrow pipecross-section so as to provide as large an evaporation area as possible.The expander 108 will have the shape of a funnel, i.e. the shape of arotation paraboloid of any configuration. It may have round or squaretransitions. The only thing that is critical is that the cross-sectiondirected into the evaporation chamber 100, or the area facing theevaporation chamber 100, is larger than the cross-sectional area of theriser pipe so as to improve the evaporation process. If one assumes thatabout 1 l per second flows upward into the evaporation chamber throughthe riser pipe, about 4 ml per second are evaporated within theevaporator at a heating power of about 10 kW. The remainder exits,cooled by about 2.5° C., via the expander 108 and ends up in acontainment collection basin 110 within the evaporation chamber. Thecontainment collection basin 110 comprises a drain 112, within which thequantity of 1 l per second, minus the evaporated 4 ml per second, isdissipated again, advantageously back to the ground water reservoir 104.For this purpose, a pump 114 or a valve for overflow control isprovided. It shall be noted that no active pumping is to be performed,since, due to gravity, water will flow downward from the evaporatorcontainment basin 110 into the ground water reservoir via a backflowpipe 113 if the pump of the valve 114 is opened. The pump or the valve114 thus ensures that the water level within the containment basin doesnot rise to too high a level or that no water vapor enters into thedrain pipe 112, and that the evaporation chamber is also securelydecoupled from the situation at the “lower” end of the backflow pipe113.

The riser pipe is arranged within a riser pipe basin 116 which is filledwith water by a pump 118 which is advantageously provided. The levels in116 and 108 are connected to one another in accordance with theprinciple of the communicating pipes, gravity and the differentpressures within 116 and 108 ensuring that the water is transported from116 to 108. The water level present in the riser pipe basin 116 isadvantageously arranged such that, even with different air pressures,the level will never fall below the inlet of the riser pipe 102 so as toprevent air from entering.

Advantageously, evaporator 10 comprises a gas separator configured toremove at least part, e.g. at least 50% of a gas dissolved in the waterto be evaporated, from the water to be evaporated, so that the removedpart of the gas will not be sucked in by the compressor via theevaporation chamber. Advantageously, the gas separator is arranged tofeed the removed part of the gas to a non-evaporated water so that thegas is transported off by the non-evaporated water. Dissolved gases maybe oxygen, carbon dioxide, nitrogen, etc. These gases evaporate mostlyat a higher pressure than water does, so that the gas separator may bearranged downstream from the expander 108, so that oxygen etc., whichhas been evaporated within the gas separator, will exit from the waterwhich has just not been evaporated yet, and will advantageously be fedinto the return pipe 113. Feeding-in is advantageously performed at thatlocation of the return pipe 113 at which the pressure is so low that thegas is again taken along into the ground water by the back-flowingwater. Alternatively, the separated gas may also be collected and bedisposed of at specific intervals or be constantly vented, i.e. releasedto the atmosphere.

Typically, the ground water, sea water, river water, lake water, thebrine or any other naturally occurring aqueous solution will have atemperature of between 8° C. and 12° C. By lowering the temperature of 1l of water by 1° C., a power of 4.2 kW may be generated. If the water iscooled by 2.5° C., a power of 10.5 kW is generated. Advantageously, acurrent of water with a current intensity depending on the heat power,in the example one liter per second, flows through the riser pipe.

If the heat pump works at a relatively high load, the evaporator willevaporate about 6 ml per second, which corresponds to a vapor volume ofabout 1.2 cubic meters per second. Depending on the heating-system watertemperature called for, the dynamic-type compressor is controlled withregard to its compression power. If a heating advance flow temperatureof 45° C. is desired, which is largely sufficient even for extremelycold days, the dynamic-type compressor will have to increase thepressure, which may have been generated at 10 hPa, to a pressure of 100hPa. If, on the other hand, an advance flow temperature of, e.g., 25° issufficient for the floor heating system, the compression that may beeffected by the dynamic-type compressor only will have a factor of 3.

The power generated is thus determined by the compressor rating, i.e.,on the one hand, by the compression factor, i.e. the degree to which thecompressor compresses and, on the other hand, by the volume flowgenerated by the compressor. If the volume flow increases, theevaporator will have to evaporate more, the pump 118 transporting moreground water into the riser pipe basin 116, so that more ground water isfed to the evaporation chamber. On the other hand, if the dynamic-typecompressor provides a lower compression factor, less ground water willflow from the bottom to the top.

However, it shall also be noted here that it is advantageous to controlthe passage of ground water through the pump 118. According to theprinciple of the communicating pipes, the filling level within container116, or the displacement capacity of the pump 118, establishes theamount of flow through the riser pipe. Therefore, an increase in theefficiency of the plant may be achieved, since the control of the flowis decoupled from the suction power of the dynamic-type compressor.

No pump might be used for pumping the ground water from below into theevaporation chamber 100. Rather, this occurs “by itself”. This automaticrise up to the evacuated evaporation chamber also assists the fact thatthe negative pressure of 20 hPa may be readily achieved. No evacuationpumps or the like might be used for this purpose. Rather, only a riserpipe having a height of more than 9 m may be used. Then a purely passivenegative-pressure generation is achieved. However, the negative pressureinvolved may also be generated using a considerably shorter riser pipe,for example when the implementation of FIG. 5 a is employed. In FIG. 5a, a considerably shorter “riser pipe” is shown. Converting highpressure to the negative pressure is accomplished via a turbine 150, theturbine withdrawing energy from the working medium in this context. Atthe same time, the negative pressure on the backflow side is againreturned to the high pressure, the energy involved in this beingsupplied by a pump 152. The pump 152 and the turbine 150 are coupled toone another via a force coupling 154, so that the turbine drives thepump, specifically using the energy that the turbine has withdrawn fromthe medium. A motor 156 merely may still be used for compensating forthe losses which the system inevitably will have, and to achieve thecirculation, i.e. to bring a system from its resting position into thedynamic mode depicted in FIG. 5 a.

In the advantageous embodiment, the dynamic-type compressor isconfigured as a radial-flow compressor with a rotatable wheel, it beingpossible for the wheel to be a slow-speed radial-flow wheel, amedium-speed radial-flow wheel, a half-axial flow wheel or an axial flowwheel, or a propeller, as are known in the prior art. Radial-flowcompressors are described in “Strömungsmaschinen”, C. Pfleiderer, H.Petermann, Springer-Verlag, 2005, pp. 82 and 83. Thus, such radial-flowcompressors comprise, as the rotatable wheel, the so-called centerrunner, the form of which depends on the individual requirements.Generally, any dynamic-type compressors may be employed, as are known asturbocompressors, fans, blowers or turbocondensers.

In the advantageous embodiment of the present invention, radial-flowcompressor 16 is configured as several independent dynamic-typecompressors which may be controlled independently at least with regardto their number of revolutions, so that two dynamic-type compressors mayhave different numbers of revolutions. Such an implementation isdepicted in FIG. 6 a, wherein the compressor is configured as a cascadeof n dynamic-type compressors. At various locations downstream from thefirst dynamic-type compressor, provision is advantageously made of oneor even more heat exchangers, for example for heating processed water,which are designated by 170. These heat exchangers are configured tocool the gas which has been heated up (and compressed) by a precedingdynamic-type compressor 172. Here, overheating enthalpy is sensiblyexploited to increase the efficiency factor of the entire compressionprocess. The cooled gas is then compressed further using one or severaldownstream compressors, or is directly fed to the liquefier. Heat isextracted from the compressed water vapor for heating, e.g., processedwater to higher temperatures than, e.g., 40° C. However, this does notreduce the overall efficiency factor of the heat pump, but evenincreases it, since two successively connected dynamic-type compressorswith gas cooling connected in between, having a longer useful lifeachieve the useful gas pressure within the liquefier due to the reducedthermal load and while needing less energy than if a single dynamic-typecompressor without gas cooling were present.

FIG. 2 further depicts the components 1100, 1102, 1106 of the secondheat pump portion, the energy that may be used for the evaporationwithin the evaporator 1102 no longer coming—in contrast to groundwater—from a medium having a low temperature, but from a medium having avery high temperature, namely, e.g., from the waste gas stream of aburner, or a heat dissipation of a solar collector.

It shall particularly be noted in this context that in the northernlatitudes, solar collectors generate high efficiencies particularly inthe transition times between summer and winter between winter andsummer, which is all the more true if the solar collectors are operatednot only for heating processed water, but also for supporting theheating system. In the middle of summer, the solar collectors generate avery large amount of warm water.

However, in the middle of summer, the demand is not particularly high,so that the capacity of typical solar collectors is not exploited in anoptimum manner in the middle of summer, since the entire supply ofenergy generated by a solar collector cannot be stored, or can only bestored at very high expense, namely when huge hot-water tanks areprovided. In accordance with the invention, this problem is nowaddressed in that the solar collector is no longer used for heatingwater, but for evaporating highly pressurized water. The hightemperatures that may be used for this are achieved particularly well inthe middle of summer, in particular, but are not available in winter.However, it is possible also in summer to generate electrical energywith a high efficiency factor using a solar collector, namely in theform of the energy provided by the turbine. If a heat sink is used atall for operating this cycle, the heating advance flow and/or theheating backflow may no longer be input into heating a building, but maybe coupled, for example, to a heat sink in the ground so as not to allowthe liquefier temperature to rise to an excessive level.

Thus, energy may also be generated in an optimum fashion in summer bymeans of a solar collector, specifically valuable electrical energywhich may be output to the power supply network and which additionallyneed not be stored by a private household, but may be output to thepower supply network in return for high fees.

In winter, when the solar collector does not provide the useful hightemperatures for water evaporation, this may readily be generated byoperating a burner, which is employed anyhow by many households forreasons of comfort, e.g. in the form of a wood-burning fireplace. Inaddition to heating comfort, there is now also a “financial” comfort,since due to the water evaporation at a high temperature due to theburning of fuels, the current generated may be used for driving thedynamic-type compressor of the actual heating system of the building inthe form of the first portion of the heat pump, or may be used forobtaining a power supply network feed, and thus to obtain a financialoutput. It is not only in summer, but also in winter that the inventiveconcept thus provides for a reduction of the power consumption costs,and, thus, of the heating costs; due to the generation of electricalcurrent by water evaporation instead of photovoltaics, heating may beobtained at almost no cost, from an overall perspective, when solarradiation is sufficient, since electricity feed-in in summer may evencut down on the power consumption, in terms of cost, in winter.

Advantageous implementations of, in particular, the first portion of theheat pump will be addressed below.

The cascaded dynamic-type compressors operated independently areadvantageously controlled by a controller 250 which maintains, on theinput side, a target temperature within the heating circuit and, as thesituation may be, also an actual temperature within the heating circuit.Depending on the target temperature desired, the number of revolutionsof a dynamic-type compressor which is arranged upstream in the cascadeand is referred to by n1, by way of example, and the number ofrevolutions n2 of a dynamic-type compressor which is arranged downstreamin the cascade are changed such as is depicted by FIG. 6 b. If a highertarget temperature is input into the controller 250, both numbers ofrevolutions are increased. However, the number of revolutions of thedynamic-type compressor arranged upstream, which is referred to by n1 inFIG. 6 b, is increased with a smaller gradient than the number ofrevolutions n2 of a dynamic-type compressor arranged downstream in thecascade. This results in that—when the ratio n2/n1 of the two numbers ofrevolutions is plotted—a straight line having a positive slope resultsin the diagram of FIG. 6 b.

The point of intersection between the numbers of revolutions n1 and n2which are individually plotted may occur at any point, i.e. at anytarget temperature, or may not occur, as the case may be. However, it isgenerally advantageous to increase a dynamic-type compressor arrangedcloser to the liquefier within the cascade more highly, with regard toits number of revolutions, than a dynamic-type compressor arrangedupstream in the cascade, should a higher target temperature be desired.

The reason for this is that the dynamic-type compressor arrangeddownstream in the cascade may process further already compressed gaswhich has been compressed by a dynamic-type compressor arranged upstreamin the cascade. In addition, this ensures that the vane angle of vanesof a radial-flow wheel, as is also discussed with reference to FIGS. 6 cand 6 d, is positioned as favorably as possible with regard to the speedof the gas to be compressed. Thus, the setting of the vane angle onlyconsists in optimizing a compression of the in-flowing gas which is aslow in eddies as possible. The further parameters of the angle setting,such as gas throughput and compression ratio, which otherwise would haveenabled a technical compromise in the selection of the vane angle, andthus would have enabled an optimum efficiency factor at a targettemperature only, are brought, in accordance with the invention, to theoptimum operating point by the independent revolutions control, andtherefore have no longer any influence on the selection of the vaneangle. Thus, an optimum efficiency factor results despite an fixedly setvane angle.

In this regard, it is advantageous, in addition, for a dynamic-typecompressor which is arranged more in the direction of the liquefierwithin the cascade to have a rotational direction of the radial-flowwheel which is opposed to the rotational direction of the radial-flowwheel arranged upstream in the cascade. Thus, an almost optimum entryangle of the vanes of both axial flow wheels in the gas stream may beachieved, such that a favorable efficiency factor of the cascade ofdynamic-type compressors occurs not only within a small targettemperature range, but within a considerably broader target temperaturerange of between 20 and 50 degrees, which is an optimum range fortypical heating applications. The inventive revolutions control and, asthe case may be, the use of counter-rotating axial flow wheels thusprovides an optimum match between the variable gas stream at a changingtarget temperature, on the one hand, and the fixed vane angles of theaxial flow wheels, on the other hand.

In advantageous embodiments of the present invention, at least one oradvantageously all of the axial flow wheels of all dynamic-typecompressors are made of plastic having a tensile strength of more than80 MPa. An advantageous plastic for this purpose is polyamide 6.6 withinlaid carbon fibers. This plastic has the advantage of having a hightensile strength, so that axial flow wheels of the disturbancecompressors may be produced from this plastic and may nevertheless beoperated at high numbers of revolutions.

Advantageously, axial flow wheels are employed in accordance with theinvention, as are shown, for example, at reference numeral 260 in FIG. 6c. FIG. 6 c depicts a schematic top view of such a radial-flow wheel,while FIG. 6 d depicts a schematic cross-sectional view of such aradial-flow wheel. As is known in the prior art, a radial-flow wheelcomprises several vanes 262 extending from the inside to the outside.The vanes fully extend toward the outside, with regard to axis 264 ofthe radial-flow wheel, from a distance of a central axis 264, thedistance being designated by rW. In particular, the radial-flow wheelincludes a base 266 as well as a cover 268 directed toward the suctionpipe or toward a compressor of an earlier stage. The radial-flow wheelincludes a suction opening designated by r1 to suck in gas, this gassubsequently being laterally output by the radial-flow wheel, as isindicated at 270 in FIG. 6 d.

When looking at FIG. 6 c, the gas in the rotational direction beforefrom the vane 262 has a higher relative speed, while it has a reducedspeed behind from the vane 262. However, for high efficiency and a highefficiency factor it is advantageous for the gas to be laterally ejectedfrom the radial-flow wheel, i.e. at 270 in FIG. 6 d, everywhere with asuniform a speed as possible. For this purpose, it is desirable to mountthe vanes 262 as tightly as possible.

For technical reasons, however, it is not possible to mount vanes whichextend from the inside, i.e. from the radius rW, to the outside astightly as possible, since the suction opening having the radius r1 thenwill become more and more blocked.

It is therefore advantageous, in accordance with the invention, toprovide vanes 272 and 274 and 276, respectively, which extend over lessthan the length of vane 262. In particular, the vanes 272 do not extendfrom rW fully to the outside, but from R1 to the exterior with regard tothe radial-flow wheel, R1 being larger than rW. By analogy therewith, asis depicted by way of example in FIG. 6 c, vanes 274 only extend from R2to the exterior, whereas vanes 276 extend only from R3 to the outside,R2 being larger than R1, and R3 being larger than R2.

These ratios are schematically depicted in FIG. 6 d, a double hatching,for example within area 278 in FIG. 6 d, indicating that there are twovanes in this area which overlap and are therefore marked by thedouble-hatched area. For example, the hatching from the bottom left tothe top right, shown in area 278, designates a vane 262 extending fromrW to the very outside, whereas the hatching extending from the top leftto the bottom right in area 278 indicates a vane 272 which extends onlyfrom r 1 to the outside in relation to the radial-flow wheel.

Thus, at least one vane is advantageously arranged between two vanesextending further to the inside, said one vane not extending so fartoward the inside. This results in that the suction area is not plugged,and/or that areas having a smaller radius are not too heavily populatedwith vanes, whereas areas having a larger radius are more denselypopulated with vanes, so that the speed distribution of the exiting gaswhich exists at the output of the radial-flow wheel, i.e. where thecompressed gas leaves the radial-flow wheel, is as homogeneous aspossible. With the inventive advantageous radial-flow wheel in FIG. 6 c,the speed distribution of the exiting gas is particularly homogeneous atthe outer periphery, since the distance of vanes accelerating the gasand due to the “stacked” arrangement of the vanes is considerablysmaller than in a case where, for example, only vanes 262 are presentwhich extend from the very inside to the very outside, and thus may havea very large distance at the outer end of the radial-flow wheel, thedistance being considerably larger than in the inventive radial-flowwheel as is depicted in FIG. 6 c.

It shall be noted at this point that the relatively expensive andcomplicated shape of the radial-flow wheel in FIG. 6 c may be producedin a particularly favorable manner by plastic injection molding, itbeing possible, in particular, to simply achieve that all vanes,including the vanes which do not extend from the very inside to the veryoutside, i.e. vanes 272, 274, 276, are fixedly anchored, since they areconnected both to the cover 268 and to the base 266 of FIG. 6 d. The useof plastic in particular with the plastic injection molding techniqueenables production of any shapes desired in a precise manner and at lowcost, which is not readily possible or is possible only at very highexpense, or is possibly not even possible at all, with axial flow wheelsmade of metal.

It shall be noted at this point that very high numbers of revolutions ofthe radial-flow wheel are advantageous, so that the acceleration actingupon the vanes takes on quite considerable values. For this reason it isadvantageous that particularly the shorter vanes 272, 274, 276 befixedly connected not only to the base but also to the cover, such thatthe radial-flow wheel may readily withstand the accelerations occurring.

It shall also be noted in this context that the use of plastic isfavorable also because of the superior impact strength of plastic. Forexample, it cannot be ruled out that ice crystals or water droplets willhit the radial-flow wheel at least of the first compressor stage. Due tothe large accelerations, very large impact forces result here whichplastics having sufficient impact strength readily withstand. Inaddition, the liquefaction within the liquefier advantageously occurs onthe basis of the cavitation principle. Here, small vapor bubblescollapse, on the basis of this principle, within a volume of water. Froma microscopic point of view, quite considerable speeds and forces arisethere which may lead to material fatigue in the long run, but which canbe readily controlled when using a plastic having sufficient impactstrength.

The compressed gas output by the last compressor 174, i.e. thecompressed water vapor, is then fed to the liquefier 18 which may beconfigured such as is depicted in FIG. 2, but which is advantageouslyconfigured such as is shown in FIG. 3 a. The liquefier 18 containsvolume of water 180 and advantageously a volume of steam 182 which maybe as small as is desired. The liquefier 18 is configured to feed thecompressed vapor into the water of the water volume 180, so that acondensation immediately results where the steam enters into the liquid,as is schematically drawn at 184. To this end, it is advantageous forthe gas supply to have an expansion area 186, such that the gas isdistributed over as large an area as possible within the liquefier watervolume 180. Typically, because of the temperature layers, the highesttemperature within a water tank will be at the top, and the coolesttemperature will be at the bottom. Therefore, the heating advance flowwill be arranged, via a floater 188, as close to the surface of thewater volume 180 as possible so as to extract the warmest water from theliquefier water volume 180. The heating backflow is fed to the liquefierat the bottom, so that the vapor to be liquefied comes in contact withwater which is as cool as possible and which moves, due to thecirculation using a heating circulating pump 312, again from the bottomin the direction of the steam-water border of the expander 186.

The embodiment in FIG. 2, wherein only a simple circulating pump 312exists, is sufficient when the liquefier is arranged in a building suchthat the areas to be heated are located below the liquefier, so that,due to gravitation, all heating pipes have a pressure which is largerthan that in the liquefier.

By contrast, FIG. 5 b shows an implementation of a connection of aheating line to the liquefier having a turbine/pump combination if theliquefier is to be arranged at a height lower than that of the heatingline, or if a conventional heating which involves a higher pressure isto be connected. Thus, if the liquefier is to be arranged at a lowerheight, i.e. below an area to be heated, and/or below the heating line300, the pump 312 will be configured as a driven pump as is shown at 312in FIG. 5 b. In addition, a turbine 310 will be provided within theheating backflow 20 b for driving the pump 312, the turbine 310 beingwired to the pump 312 via a force coupling 314. The high pressure willthen be present within the heating system, and the low pressure will bepresent within the liquefier.

Since the water level within the liquefier would rise more and more dueto the vapor being constantly introduced into the liquefier, the drain22 is provided, via which, e.g., about 4 ml per second may also drainoff for the water level within the liquefier to essentially not change.To this end, a drain pump, or a drain valve, 192 for pressure regulationis provided, such that without pressure loss, the useful amount of,e.g., 4 ml per second, i.e. the quantity of water vapor which is fed tothe liquefier while the compressor is running, is drained off again.Depending on the implementation, the drain may be introduced into theriser pipe as is shown at 194. Since all kinds of pressures between onebar and the pressure existing within the evaporation chamber are presentalong the riser pipe 102, it is advantageous to feed in the drain 22into the riser pipe at that location 194 where roughly the same pressureexists as it exists downstream from the pump 192, or valve 192. Then, nowork has to be done to re-feed the drain water to the riser pipe.

In the embodiment shown in FIG. 2, one operates completely without anyheat exchanger. The ground water is thus evaporated, the vapor is thenliquefied within the liquefier, and the liquefied vapor is eventuallypumped through the heating system and re-fed to the riser pipe. However,since only a (very small) part of, rather than all of, the quantity ofwater flowing through the riser pipe is evaporated, water which hasflown through the floor heating system is thus fed to the ground water.If something like this is prohibited according to communal regulations,even though the present invention entails no contamination whatsoever,the drain may also be configured to feed the amount of 4 ml per second,which corresponds to roughly 345 l per day, to the sewage system. Thiswould ensure that no medium which has been present within any heatingsystem of any building is directly fed back into the ground water.

However, the backflow 112 from the evaporator may be fed to the groundwater without any problems, since the water flowing back there only wasin contact with the riser pipe and the return line, but has not exceededthe “evaporation boundary” between the evaporation expander 108 and theoutput to the dynamic-type compressor.

It shall be noted that in the embodiment shown in FIG. 2, theevaporation chamber as well as the liquefier, or the vapor chamber 182of the liquefier, may be sealed off As soon as the pressure within theevaporation chamber exceeds the mark that may be used for the waterbeing pumped through the riser pipe to evaporate, the heat pump processcomes to a “standstill”.

In the following, reference shall be made to FIG. 3 a which representsan advantageous embodiment of the liquefier 18. The feed line 198 forcompressed vapor is positioned within the liquefier such that the vapormay exit into this water volume just below the surface of the liquefierwater volume 180. For this purpose, the end of the vapor supply linecomprises nozzles arranged around the circumference of the pipe, throughwhich the vapor may exit into the water. For the mixing which occurs tobe as thorough as possible, i.e. for the vapor to come into contact withwater as cold as possible to liquefy as fast and efficiently aspossible, an expander 200 is provided. This expansion is arranged withinthe liquefier water volume 180. At its narrowest point, it has acirculating pump 202 configured to suck in cold water at the bottom ofthe liquefier and to displace it, by means of the expander, toward aflow which is directed upward and becomes broader. This is intended tocause as large quantities as possible of the vapor entering into theliquefier water 180 to contact water which is provided by thecirculating pump 202 and is as cold as possible.

In addition, it is advantageous to provide, around the liquefier, asound insulation 208 which may be configured in an active or a passivemanner. A passive sound insulation will insulate the frequencies of thesound generated by the liquefaction as well as possible, similar tothermal insulation. It is equally advantageous to subject the othercomponents of the system to the sound insulation.

Alternatively, the sound insulation may also be configured to be active,in which case it would have, for example, a microphone for soundmeasurement, and would trigger, in response thereto, a soundcountereffect, such as to cause an outer liquefier wall etc. to vibratewith, e.g., piezoelectric means.

The embodiment shown in FIG. 3 a is somewhat problematic in that theliquid 180 located within the liquefier will enter into the pipe 198,within which otherwise a compressed vapor is present, when the heat pumpis powered down. In one implementation, a backflow valve may be providedwithin line 198, for example near the output of the line from theliquefier. Alternatively, the line 198 may be directed upward,specifically so far upward that no liquid flows back into the compressorwhen the compressor is switched off. When the compressor is powered upagain, the water from the vapor line 198 will initially be pressed intothe liquefier by the compressed vapor.

Not until a sufficient portion of the water has been removed from theline 198 will a vapor be made to condensate within the liquefier. Anembodiment of such a type thus has a certain delay time which is usefuluntil the water volume 180 is heated up again by the compressed vapor.In addition, the work useful for removing the water which has enteredinto the line 198 from the line 198 again is no longer retrievable andis thus “lost” with regard to the heating system, such that small-scalelosses in terms of the efficiency factor may have to be accepted.

An alternative embodiment which overcomes this problem is shown in FIG.3 b. Unlike in FIG. 3 a, the compressed vapor is now not fed within apipe below the water level within the liquefier. Instead, the vapor is“pumped”, as it were, into the liquid within the liquefier from thesurface. For this purpose, the liquefier includes a nozzle plate 210comprising nozzles 212 which project in relation to the plane of thenozzle plate 210. The nozzles 212 extend below the water level of thewater volume 180 in the liquefier. The recessed portions between twonozzles, shown at 214 in FIG. 3 b, by contrast extend above the waterlevel of the water volume 180 within the liquefier, so that the watersurface of the liquefier water, the water surface being interrupted by anozzle, is located between two nozzles. The nozzle 212 has nozzleopenings through which the compressed vapor which spreads from the line198 within the vapor volume 182 may enter into the liquefier water, asis schematically shown by arrows 216.

If, in the implementation of FIG. 3 b, the compressor is powered down,this will result in that the liquid enters into the nozzles 212 of thenozzle plate 210 to a small extent only, so that very little work may bedone in order to press the water out from the nozzles again when theheat pump is powered up again. At any rate, the expander 200 ensuresthat, due to being fed through the expander, the liquid transportedupward by the pump 202 is as cold as possible and comes into contactwith the warm vapor. Then the warm water will either immediately enterinto the advance flow 20 a, or it will spread within the water volumeover the expander edge, as is depicted by an arrow 218, so that atemperature stratification which is disturbed to as small an extent aspossible, in particular because of the shape of the expander, will occurwithin the liquefier outside the expander.

The flow rate present at the edge of the expander, i.e. where arrow 218is indicated, is considerably lower than in the center. It isadvantageous to operate the liquefier as a temperature layer storagesuch that the heat pump and, in particular, the compressor need not runwithout interruption, but may run only when there is a need, as is alsothe case for normal heating installations operating, for example, withan oil burner.

FIG. 3 c shows a further advantageous implementation of the liquefier ina schematic form. In particular, the liquefier comprises a gas separator220 coupled to the gas volume 182 within the liquefier. Any gas arisingwithin the liquefier, such as oxygen or another gas which may leakwithin the liquefier, collects within the gas-separator container 220.By actuating a pump 222, advantageously at certain intervals, sincepermanent gas evacuation might not be used due to the small quantity ofgas developing, this gas may then be pumped into the atmosphere.Alternatively, the gas may also be docked into the backflow 112 or 113of FIG. 2 again, so that the gas is again brought back into the groundwater reservoir, along with the ground water flowing back, where it willagain be dissolved within the ground water, or will merge into theatmosphere when it enters into the ground water reservoir.

Since the inventive system operates with water, no gases will develop,even with a high gas leakage, which have not already been dissolvedwithin the ground water previously, so that the gas separated offentails no environmental problems whatsoever. It shall again beemphasized that, due to the inventive dynamic-type compressorcompression and due to the use of water as the working fluid, there willbe no contamination or soiling by synthetic coolants or by oil, due toan oil cycle, at any point. As the working medium, the inventive systemat any point has water or vapor, which is at least as clean as theoriginal ground water, or is even cleaner than the ground water due tothe evaporation within the evaporator, since the water is distilledwater once the compressed vapor has been liquefied again within theliquefier.

In the following, an advantageous embodiment of the evaporator will bedepicted with reference to FIG. 4 a so as to advantageously employ theliquefier drain to accelerate the evaporation process. For this purpose,the drain, which, as one knows, has the temperature of the heatingsystem backflow, i.e. has a much higher temperature than the groundwater pumped from the earth, is passed through the expander 108 of theevaporator, so that the wall of the drain pipe 204 acts as a nucleus fornucleate boiling. Thus, a substantially more efficient vapor isgenerated by the evaporator than if no such nucleating action wereprovided. In addition, it is advantageous to configure the wall of thedrain pipe 204, at least within the expander, to be as structured aspossible, as is depicted at 206, to improve the nucleation for thenucleate boiling even more. The rougher the surface of the drain pipe204, the more nuclei will be generated for nucleate boiling. It shall benoted that the flow through the drain pipe 22 is only very low, sincewhat is dealt with here is only the 4 ml per second which are fed to theliquefier in one mode of operation. Nevertheless, the considerably moreefficient nucleate boiling may be caused already with this small amountand because of the temperature, which is relatively high as compared tothe ground water, so as to reduce the size of the evaporator whilemaintaining the efficiency of the heat pump.

To accelerate the evaporation process, alternatively or additionally, anarea of the evaporator which has water which is to be evaporated locatedthereon, i.e. the surface of the expander or a part thereof, may beconfigured from a rough material to provide nuclei for nucleate boiling.Alternatively or additionally, a rough grate may also be arranged (closeto) below the water surface of the water to be evaporated.

FIG. 4 b shows an alternative implementation of the evaporator. Whilethe drain in FIG. 4 a has been employed merely as a “flow-through”assistance of the nucleate formation for efficient evaporation, and, ashas been depicted on the left-hand side in the picture in FIG. 4 a, thedrain is drained off once it has passed through the evaporator, thedrain in FIG. 4 b is itself used for reinforcing the nucleate formation.For this purpose, the liquefier drain 22 of FIG. 2 is connected to anozzle pipe 230, possibly via a pump 192 or, if conditions permit,without a pump, the nozzle pipe 230 having a seal 232 on one end andhaving nozzle openings 234. The warm liquefier water drained from theliquefier via drain 22 at a rate of, for example, 4 ml per second is nowfed into the evaporator. On its way to a nozzle opening 234 within thenozzle pipe 230, or immediately at the exit of a nozzle, it will alreadyevaporate, as it were, below the water surface of the evaporator waterbecause of the pressure which is too low for the temperature of thedrain water.

The vapor bubbles forming there will immediately act as boiling nucleifor the evaporator water which is pumped via the inflow 102. Thus,efficient nucleate boiling may be triggered within the evaporatorwithout any major additional measures being taken, this triggeringexisting, similar to FIG. 4 a, because of the fact that the temperaturenear the rough area 206 in FIG. 4 a or near a nozzle opening 234 isalready so high that, given the existing pressure, evaporation willimmediately take place. This evaporation forces the generation of asmall vapor bubble which, if the conditions are favorably selected, willhave a very high probability of not collapsing again, but of developinginto a vapor bubble which goes to the surface and which, once it hasentered into the vapor volume within the evaporation chamber, will besucked off by the compressor via the suction pipe 12.

The embodiment shown in FIG. 4 b involves the liquefier water to bebrought into the ground water cycle, since the medium exiting the nozzlepipe 230 eventually will re-enter into the backflow 112 via the overflowof the evaporator, and will thus be made to contact the ground water.

If there are water-regulatory provisions or any other reasons why thisis not admissible, the embodiment shown in FIG. 4 c may be employed. Thewarm liquefier water provided by the liquefier drain 22 is introducedinto a heat exchanger 236 at a rate of, e.g., 4 ml per second to giveoff its heat to ground water which has been branched off from the mainground water stream within line 102 via a branch line 238 and abranching-off pump 240. The branched-off ground water will thenessentially take on the heat of the liquefier drain within the heatexchanger 236, so that pre-heated ground water is introduced into thenozzle pipe 230, for example at a temperature of 33° C. so as toeffectively trigger or support the nucleate boiling within theevaporator by means of the temperature which is high compared to theground water. On the other hand, the heat exchanger provides, via adrain line 238, drain water which is cooled to a relatively high extentand which is then fed to the sewage system via a drain pump 240. On thebasis of the combination of the branch line 238 and the branching-offpump 240 and the heat exchanger 236, only ground water is used in, orintroduced into, the evaporator without said ground water having been incontact with any other medium. Thus, there is no water-regulatoryrelevance associated with the embodiment shown in FIG. 4 c.

FIG. 4 d shows an alternative implementation of the evaporator with edgefeeding. Unlike in FIG. 2, here the expander 200 of the evaporator isarranged below the water level 110 within the evaporator. This causeswater to flow toward the center of the expander “from outside” so as tobe returned in a central line 112. While the central line in FIG. 2 hasserved to feed the evaporator, in FIG. 4 d it now serves to drain offthe non-evaporated ground water. By contrast, the line 112 shown in FIG.2 has served to drain off non-evaporated ground water. In FIG. 4 d, bycontrast, this line at the edge serves as a ground water feed.

FIG. 4 e shows an advantageous implementation of the expander 200 as maybe employed within the evaporator, or of the expander as may also beemployed, e.g., within the liquefier and as is shown, for example, inFIG. 2 or FIG. 3 a or 3 b, respectively. The expander is advantageouslyconfigured such that its small diameter advantageously enters into theexpander in the center of the “large” expander area. This diameter ofthis inflow or drain (in FIG. 4 d) advantageously ranges between 3 and10 cm and, in particularly advantageous embodiments, between 4 and 6 cm.

The large diameter d2 of the expander ranges between 15 and 100 cm inadvantageous embodiments, and is smaller than 25 cm in particularlyadvantageous embodiments. The small configuration of the evaporator ispossible if efficient measures for triggering and assisting nucleateboiling are employed, as has been explained above. The small radius dland the large radius d2 have an area of curvature of the expanderlocated between them which is advantageously configured such that withinthis area a laminar flow results which is decreased from a fast flowrate, advantageously within the range from 7 to 40 cm per second, to arelatively small flow rate at the edge of the expander. Largediscontinuities of the flow rate, for example eddies within the area ofthe line of curvature, or “bubbling effects” above the inflow, if theexpander is viewed from the top, are advantageously avoided since theymay possibly have a negative effect on the efficiency factor.

In particularly advantageous embodiments, the expander has a shape whichresults in that the height of the water level above the expander surfaceis smaller than 15 mm and is advantageously between 1 and 5 mm. It istherefore advantageous to employ an expander 200 configured such that inmore than 50% of the area of the expander, when viewed from the top, awater level exists which is smaller than 15 mm. Thus, efficientevaporation may be ensured across the entire area which is evenincreased, it terms of its efficiency, when measures for triggeringnucleate boiling are used.

Thus, the inventive heat pump serves to efficiently supply buildingswith heat, and it no longer involves any working substance whichnegatively affects the world climate. In accordance with the invention,water is evaporated under very low pressure, is compressed by one orseveral dynamic-type compressors arranged one behind the other, and isagain liquefied into water. The transported energy is used for heating.In accordance with the invention, use is made of a heat pump whichadvantageously represents an open system. Here, open system means thatground water or any other available aqueous medium carrying heat energyis evaporated, compressed and liquefied under low pressure. The water isdirectly used as the working substance. Thus, the energy contained isnot transmitted to a closed system. The liquefied water isadvantageously used directly within the heating system and issubsequently supplied back to the ground water. To capacitively decouplethe heating system, it may also be terminated by a heat exchanger.

The efficiency and usefulness of the present invention is represented bymeans of a numerical example. If one assumes an annual heatingrequirement of 30,000 kWh, in accordance with the invention aboutmaximally 3,750 kWh of electrical current may be expended for operatingthe dynamic-type compressor to achieve this, since the dynamic-typecompressor need only provide about an eighth of the entire amount ofheat that may be useful.

The eighth results from the fact that a sixth needs to be expended inthe event of extreme cold only, and that, for example, at transitiontemperatures such as in March or at the end of October, the efficiencyfactor may rise to a value of more than 12, so that, on average, amaximum of one eighth may be expended over the year.

At electricity prices of about 10 eurocents per kWh, which may bearrived at for electricity if one buys electricity for which the powerstation need not guarantee that operation will be free frominterruptions, this roughly corresponds to annual costs of 375 euros. Ifone wants to generate 30,000 kWh using oil, one would need about 4,000l, which would correspond to a price of 2,800 euros on the basis ofcurrent oil prices, which are very unlikely to fall in the future. Inaccordance with the invention, one can therefore save 2,425 euros perannum! In addition, it shall also be pointed out that in comparison withburning oil or gas for heating purposes, up to 70% of the amount of CO2released is saved by means of the inventive concept.

To reduce the manufacturing cost and also to reduce the maintenance andassembly costs, it is advantageous to configure the housings of theevaporator, of the compressor and/or of the liquefier and also,particularly, the radial-flow wheel of the dynamic-type compressor, fromplastic, and in particular from injection molding plastic. Plastic iswell suited since plastic is corrosion-resistant with regard to water,and since, in accordance with the invention, the maximum temperaturesare advantageously clearly below the deformation temperatures ofemployable plastics compared to conventional heating systems. Inaddition, assembly is particularly simple since negative pressure ispresent within the system consisting of evaporator, compressor andliquefier. Thus, substantially fewer requirements are placed on thesealings since the entire atmospheric pressure assists in keeping thehousings leak-proof. Also, plastic is particularly well suited since atno location in the inventive system are there high temperatures whichwould involve the use of expensive special plastics, metal or ceramic.By means of plastic injection molding, the shape of the radial-flowwheel may also be optimized in any manner desired while beingmanufactured in a simple manner and at low cost despite its complicatedshape.

Depending on the circumstances, the inventive method may be implementedin hardware or in software. Implementation can be on a digital storagemedium, in particular a disk or CD, with electronically readable controlsignals which may interact with a programmable computer system such thatthe respective method is performed. Generally, the invention thus alsoconsists in a computer program product with a program code, stored on amachine-readable carrier, for performing the inventive method when thecomputer program product runs on a computer. In other words, theinvention may thus be realized as a computer program having a programcode for performing the method when the computer program runs on acomputer.

In accordance with an embodiment of the present water pump, samecomprises, in the first portion, an evaporator 10, which may be coupledto a heat source, a dynamic-type compressor 16 configured to consumeelectrical current, and the liquefier 18, the heat source beingdimensioned such that the working fluid evaporates at the firstpressure.

In an advantageous embodiment of the water pump, the evaporator 100 isconfigured to evaporate water which is present in the environment in theform of ground water, sea water, river water, lake water or brine, andthe liquefier 18 is configured to feed liquefied water to theevaporator, to the soil or to a water treatment plant.

In an advantageous embodiment of the water pump, the compressor 16 isconfigured to compress the working vapor to a working pressure higherthan 25 hPa.

In an advantageous embodiment of the water pump, the dynamic-typecompressor is configured as a radial-flow compressor.

In an advantageous embodiment of the water pump, the evaporator 10comprises a riser pipe 102 coupled to the evaporation chamber 100, oneend of the riser pipe 102 being connected to a liquid-filled container116 for the working liquid, and the other end of the riser pipe 102being connected to the evaporation chamber 100 so that the evaporationpressure results within the evaporation chamber 100 due to the effect ofgravitation.

In an advantageous embodiment of the water pump, the riser pipe 102 isconfigured to have a height of more than 8 m.

In an advantageous embodiment of the water pump, the evaporatorcomprises a turbine 150, via which a pressure of an upstreaming workingfluid is reduced, and which extracts energy from the working liquid inthe process, the turbine 150 further being operatively coupled to a pump152 to bring a downstreaming working liquid from the pressure presentwithin the evaporation chamber to the pressure of the upstreamingworking fluid, the operative coupling 154 being configured such that thepump 152 uses at least part of the energy the turbine has extracted.

In an advantageous embodiment of the water pump, the evaporator 10comprises: an expander 108 which expands, within the evaporationchamber, to at least three times a diameter of a feed line to theevaporation chamber; a reception apparatus 110 configured to receive anyworking liquid overflowing over an edge of the expander 108; and a drainmeans 112 configured to carry off the overflowing working liquid.

In an advantageous embodiment of the water pump, the drain means 112 iscoupled to a flow control means 114, the flow control means 114 beingcontrollable to maintain a level of the overflowing working liquidwithin the reception apparatus 110 within a predefined range.

In an advantageous embodiment of the water pump, the evaporator 10comprises a gas separator configured to remove at least part of a gasdissolved in the water to be evaporated from the water to be evaporated,so that the removed part of the gas is not sucked in by the compressorvia the evaporation chamber.

In an advantageous embodiment of the water pump, the gas separator isarranged to feed the removed part of the gas to non-evaporated water sothat the gas is transported off by the non-evaporated water.

In an advantageous embodiment of the water pump, the evaporator 10comprises: an expander 200 which expands, within the evaporationchamber, to at least three times a diameter of a drain 112 outside theevaporation chamber 100; a reception apparatus configured to receive theworking liquid fed to the evaporation chamber; and an inflow means tosupply the reception apparatus with ground water; the expander beingarranged within the evaporation chamber such that working fluid flowsoff, over an edge of the expander comprising a large diameter, to anarea of the expander comprising a low diameter, and from there via adrainage.

In an advantageous embodiment of the water pump, the liquefier comprisesa gas separator 220, 222 to drain off, from a separator volume 220, anygas accumulating within the liquefier which differs from water vapor.

In an advantageous embodiment of the water pump, the liquefier 18comprises a drain 22 to drain off liquefied working liquid, and thedrain 22 comprises a portion 204 arranged within the evaporator forproviding a nucleating effect for a bubble evaporation within theevaporator.

In an advantageous embodiment of the water pump, a portion 204 of adrain for water from the liquefier comprises a roughness area 206 whichhas a surface roughness which is at least such that a nucleating effectfor a nucleate formation is increased as compared with a smooth surfaceof the drain in the form of a common pipe.

In an advantageous embodiment of the water pump, the drain 22 is coupledto a nozzle pipe 230 which comprises nozzle openings 234 to feed aworking fluid located within the nozzle pipe 230 into water which is tobe evaporated and is located within the evaporator, so as to provide anucleating effect for a bubble evaporation within the evaporator.

In an advantageous embodiment of the water pump, the evaporatorcomprises a heat exchanger 236, a branch line 238 for feeding the heatexchanger, and a heat-exchanger drain coupled to a nozzle pipe 230 whichcomprises nozzle openings 234, and the heat exchanger 236 being coupled,on the input side, to a liquefier drain 22, so that a warmth of a liquiddispensed by the liquefier drain 22 is transmitted to a working fluidfed to the nozzle pipe 230, so as to provide a nucleating effect for abubble evaporation within the evaporator.

In an advantageous embodiment of the water pump, the liquefier 18comprises a drain 22 for draining off liquefied working liquid, thedrain being coupled, at a coupling position 194, to the riser pipe 102or to a backflow pipe 113, where a liquid pressure within the riser pipeor the backflow pipe 113 is smaller than or equal to a pressure presentat the drain 22.

In an advantageous embodiment of the water pump, the liquefier 18comprises a drain 22 for draining off liquefied working liquid, thedrain being coupled, at a coupling position 194, to the riser pipe 102or to a backflow pipe 113, a pressure compensation means 192 beingarranged between the drain 22 from the liquefier 18 and the couplingposition 194, the pressure compensation means 192 being configured tocontrol a pressure of the water drained off from the liquefier 18 suchthat the water will enter into the riser pipe 102 or into the backflowpipe 192.

In an advantageous embodiment of the water pump, the liquefier 18comprises a drain 22 which comprises a pump 192 configured to increase apressure of water drained off from the liquefier to such a pressure thatthe water drained off may enter into a sewage system or seep into soilon a property.

In an advantageous embodiment of the water pump, the compressor 16comprises a rotatable wheel which is configured as a radial-flow wheel,a half-axial flow wheel, an axial flow wheel or a propeller and may bedriven to compress the working vapor.

In an advantageous embodiment of the water pump, the liquefier 18comprises a liquefier chamber which may be filled up at least partiallywith the liquefier water volume 180 and which is further configured tomaintain the water level above a minimum level.

In an advantageous embodiment of the water pump, the liquefier 18comprises a vapor supply line 198 coupled to an output of the compressor16, the vapor supply line being arranged within the water volume 180such that the vapor may enter into the water volume 180 beneath acurrent water level.

In an advantageous embodiment of the water pump, the liquefier 18 isconfigured to feed the compressed vapor to the liquefier via a pipearranged below a water surface within the liquefier, the pipe comprisingnozzle openings, so that the vapor enters into a water volume within theliquefier via an area determined by the nozzle openings.

In an advantageous embodiment of the water pump, the liquefier comprisesa nozzle plate 210 comprising projecting nozzle openings 212, the nozzleplate being arranged within the liquefier, with regard to the watervolume 180, such that a water level within the liquefier is positionedbetween a projecting nozzle opening 212 and the nozzle plate 210.

In an advantageous embodiment of the water pump, the liquefier 18comprises a circulating pump 202 for circulating liquefied workingliquid to transport cold working liquid to a condensating point or totransport heat to a cold working liquid.

In an advantageous embodiment of the water pump, the liquefier comprisesa heating advance flow 20 a and a heating backflow 20 b to the liquefierwater volume 180.

In an advantageous embodiment of the water pump, a portion of theheating backflow 20 b has a turbine 310 arranged therein, via which ahigh pressure within the heating system 300 is reduced to a low pressurewithin a water volume 180 of the liquefier 180, and the energy gained inthe process is removed from the heating water, the turbine 310 furtherbeing operatively coupled to the pump 312 to bring the heating waterfrom the low pressure within the liquefier to the high pressure withinthe heating system 300, the operative coupling 314 being configured suchthat the pump 312 uses at least part of the energy the turbine 310 hasextracted.

In an advantageous embodiment of the water pump, the liquefier 18comprises a heat exchanger to decouple, in terms of liquid, a heatingsystem 300 and the liquefier.

In an advantageous embodiment of the water pump, the liquefier 18comprises an expander 200 comprising a narrow opening and a wideopening, the expander being arranged within the liquefier such that acirculating pump 202 is arranged within the narrow opening, and thecompressed vapor may be fed to the wide opening 198.

In an advantageous embodiment of the water pump, the compressor 16 isconfigured by several dynamic-type compressors arranged one behind theother to compress the working vapor to an intermediate pressure by afirst dynamic-type compressor 172, and to compress the working vapor tothe working pressure by a last dynamic-type compressor 174.

In an advantageous embodiment of the water pump, at least twodynamic-type compressors arranged one behind the other comprise axialflow wheels driven with rotational directions directed in a manneropposed to one another.

In an advantageous embodiment of the water pump, one or several heatexchangers 170 are arranged downstream from a first dynamic-typecompressor 172 or a further dynamic-type compressor 174 so as towithdraw heat from the working vapor and to heat water therewith.

In an advantageous embodiment of the water pump, the heat exchanger isconfigured to reduce the temperature of the working vapor to atemperature, at a maximum, which is higher than a temperature prior to apreceding compressor stage 172.

In an advantageous embodiment of the water pump, same further comprisesa sound insulation 208 configured such that noises within the liquefier,the evaporator or the compressor are damped by at least 6 dB.

In an advantageous embodiment of the water pump, same comprises: acontrol 250 for maintaining a target temperature, for detecting anactual temperature and for controlling the compressor 16 to increase anoutput pressure or an output volume of the compressor if the targettemperature is higher than the actual temperature, and to reduce theoutput pressure or the output volume if the target temperature is lowerthan the actual temperature.

In an advantageous embodiment of the water pump, the at least theevaporation chamber, a housing of the compressor or a housing of theliquefier, or a radial-flow wheel of the dynamic-type compressor aremade of plastic.

In an advantageous embodiment of the water pump, the dynamic-typecompressor 16 comprises a radial-flow compressor comprising aradial-flow wheel 260 which comprises a plurality of vanes 262, 272,274, 276 extending from one or several inner radii to one or severalouter radii, the vanes extending to the outside, with regard to theradial-flow wheel, from different radii R1, R2, R3, r1 of theradial-flow wheel.

In an advantageous embodiment of the water pump, the at least one vane272 is arranged between two vanes 262 extending to the outside, withregard to the radial-flow wheel 260, from a radius rW, the at least onevane 272 extending to the outside, with regard to the radial-flow wheel260, from a larger radius R1.

In an advantageous embodiment of the water pump, the radial-flow wheel260 comprises a base 266 and a cover 268, at least one vane 272 of theradial-flow wheel 260 which extends to the outside from a larger radiusR1 than another vane 262 being integrally connected both to the cover268 and to the base 266.

In an advantageous embodiment of the water pump, a temperature of thewater, which is compressed in the compression step, is lower than 80°C., and a temperature of the vapor, which is generated in theevaporating step, is higher than 120° C.

In an advantageous embodiment of the computer program comprising aprogram code for performing the method, the computer program runs on anarithmetic unit.

While this invention has been described in terms of several embodiments,there are alterations, permutations, and equivalents which fall withinthe scope of this invention. It should also be noted that there are manyalternative ways of implementing the methods and compositions of thepresent invention. It is therefore intended that the following appendedclaims be interpreted as including all such alterations, permutationsand equivalents as fall within the true spirit and scope of the presentinvention.

1. A heat pump comprising: a first portion for evaporating a workingfluid at a first pressure, for compressing the evaporated working fluidto a second, higher pressure, and for liquefying the compressed workingfluid within a liquefier; and a second portion for compressing liquidworking fluid to a third pressure, which is higher than the secondpressure, for evaporating the working fluid compressed to the thirdpressure, for relaxing the evaporated working fluid so as to generateelectrical current, and for liquefying relaxed evaporated working fluidwithin the liquefier.
 2. The heat pump as claimed in claim 1, whereinthe first portion is configured to employ, for compressing theevaporated working fluid, electrical current coming from the secondportion or from an external power supply network, and wherein the secondportion is configured to at least partly feed the electrical currentinto the external power supply network.
 3. The heat pump as claimed inclaim 1, wherein the working fluid is water.
 4. The heat pump as claimedin claim 1, wherein the first portion is configured to generate anevaporator at a first pressure smaller than 20 hPa, and to generate acompression to a second pressure which is more than 5 hPa higher thanthe first pressure.
 5. The heat pump as claimed in claim 1, wherein thesecond portion is configured to compress to a third pressure higher than0.2 MPa.
 6. The heat pump as claimed in claim 1, wherein the secondportion is configured to compress liquefied working fluid, whichoriginates from the liquefier, to the third pressure.
 7. The heat pumpas claimed in claim 1, wherein the second portion is configured toevaporate the liquid working fluid, which has been compressed to thethird pressure, while using a primary energy source, the primary energysource comprising a waste gas stream of a combustion process of a heatdissipator of a solar collector.
 8. The heat pump as claimed in claim 1,wherein the liquefier comprises two supply lines, a first supply linebeing connected to a dynamic-type compressor of the first portion, andthe second supply line being connected to a turbine of the secondportion.
 9. The heat pump as claimed in claim 1, wherein a coupler isprovided which, on the input side, comprises two supply lines, a firstsupply line being connected to a dynamic-type compressor of the firstportion, and a second supply line being connected to the turbine of thesecond portion, and which is connected, on the output side, to theliquefier, the coupler being configured to couple either the firstsupply line or the second supply line or both supply lines to theliquefier at the same time.
 10. The heat pump as claimed in claim 1,comprising a controller so as to couple, in response to a controlsignal, an output for electrical current of the turbine of the secondportion to an input for electrical energy of a dynamic-type compressorof the first portion.
 11. The heat pump as claimed in claim 1, whereinthe second portion comprises a liquid pump, an evaporator which may becoupled to a heat source, a turbine for providing electrical current,and the liquefier, the heat source being dimensioned such that theworking fluid evaporates at the third pressure.
 12. A method of pumpingheat, comprising: operating a first portion, operating the first portioncomprising evaporating a working fluid at a first pressure, compressingthe evaporated working fluid to a second, higher pressure, andliquefying a compressed working fluid within a liquefier; or operating asecond portion, the operation of the second portion comprisingcompressing liquid working fluid to a third pressure, which is higherthan the second pressure, evaporating the working fluid which has beencompressed to the third pressure, relaxing the evaporated working fluidto a pressure smaller than the third pressure, so as to generateelectrical current, and liquefying relaxed evaporated working fluidwithin the evaporator.
 13. A small power station for heating buildings,comprising: a water pump for compressing water to a first pressure above0.1 MPa; an evaporator for evaporating the compressed water usingprimary energy from a combustion process or from a solar collector so asto provide water vapor at the first pressure; a turbine for generatingelectrical current, the turbine being configured to bring water vapor upto a second pressure while outputting electrical current, the secondpressure being smaller than 50 kPa; and a liquefier for liquefying thecooled-off water vapor, the liquefier comprising a heating advance flowand a heating backflow for heating a building.
 14. A method of heating abuilding, comprising: compressing water to a first pressure above 0.1MPa; evaporating the compressed water while using primary energy from acombustion process or from a solar collector, so as to provide watervapor at the first pressure; generating electrical current by relaxingthe water vapor at the first pressure to a second pressure, the secondpressure being smaller than 50 kPa; and liquefying the water vapor,which has been output by generating electrical current, within aliquefier water volume coupled to a heating advance flow and a heatingbackflow for heating a building.